Journal of Fishery Sciences of China (中国水产科学) 2013/20:6 PP.1212-1218
Saline-alkaline water is relatively prevalent throughout China. High alkalinity is thought to represent a significant stressor for aquatic organisms that occupy saline-alkaline waters. Gymnocypris przewalskii is a commercially important fish that is endemic to Qinghai Lake, a high saline-alkali environment. This species is anadromous and migrates up rivers to spawn between April to July. The abundance of G. przewalskii has decreased dramatically because of over-fishing and habitat degradation. As a result, it is now listed as an endangered fish. Thus, an understanding of the changes in stress-related enzymes in the liver and kidney of juvenile G. przewalskii exposed to carbonate alkalinity (CA) may prove useful for protecting the remaining G. przewalskii resource. We exposed juvenile G. przewalskii to 32 or 64 mmol/L carbonate alkalinity stress and measured the activity of superoxide dismutase (SOD), acid phosphatase (ACP), and alkaline phosphatase (AKP) in the liver and kidney 0.25, 0.5, 1, 2, 3, 4, 5, 7, and 9 d after the initial exposure. SOD is involved in the elimination of reactive oxygen species, which are produced following exposure to environmental stressors, whereas ACP and AKP assist in the elimination of metabolic products by dephosphorylation. The activity of both liver and kidney SOD initially increased with exposure time then returned to control levels. Liver SOD activity peaked in the CA32 and CA64 groups on day 3, whereas kidney SOD activity peaked on days 4 and 3, respectively. Interestingly, carbonate alkalinity stress promoted ACP activity in the liver but inhibited its activity in the kidney. There was no significant change in ACP activity in the liver of the CA32 group. Conversely, levels in the CA64 group were highest on day 4. Kidney ACP activity was lowest on day 1 and peaked on day 7 in the CA32 group, but was lowest after 12 h in the CA64 group. Both liver and kidney AKP activity increased with increasing exposure time. Liver AKP activity peaked on day 1 and 3 in the CA32 and CA64 groups, respectively. Our results suggest that liver and kidney SOD, ACP, and AKP play important role in the acclimation of G. przewalskii to carbonate alkalinity stress. The activity of these three enzymes was up-regulated by exposure to carbonate alkalinity stress, but recovered to control levels within 4 d, suggesting that G. przewalskii has the ability to adapt to concentrations <64 mmol/L carbonate alkalinity. The changes in the activity of these three enzymes likely plays an important role in protecting G. przewalskii from carbonate alkalinity stress. The activity of the three enzymes was up-regulated earlier in the kidney than in the liver, suggesting that the physiological responses to carbonate alkalinity occur earlier in the kidney than in the liver. Our results provide insight into how these three enzymes participate in the response of G. prze-walskii to carbonate alkalinity stress, and provide a basis for setting water quality guidelines for the conservation of G. przewalskii.